Apparatus and method of fabricating a compensating element for wavefront correction using spatially localized curing of resin mixtures

ABSTRACT

An optical wavefront correction plate incorporates a unique, three-dimensional spatial retardation distribution utilizing the index of refraction change of resin mixture in its cured state. The optical wave plate comprises a pair of transparent plates, containing a layer of a monomers and polymerization initiators, such as resin mixture. This resin mixture exhibits a variable index of refraction as a function of the extent of its curing. Curing of the resin mixture may be made by exposure to light, such as ultraviolet light, and may be varied across and through the surface of the resin mixture to create a particular and unique three-dimensional wavefront retardation profile. The optical wave plate provides improved performance in large area mirrors, lenses, telescopes, microscopes, and ophthalmic diagnostic systems.

RELATED APPLICATIONS

A patent disclosure document of this application was filed and stampedby the U.S. Patent and Trademark Office on Dec. 27, 2000, Document No.484302.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to producing optical elementsfor use in optical systems.

2. Description of the Related Art

In many optical systems it is common to assume that the light passingthrough the system is limited to paraxial rays, specifically, rays thatare near the optical axis and that are sustained within small angles.With this assumption, corrective optics having only spherical surfacescan correct aberrations that are present in images generated by theoptical systems. While aspheric optics can be produced, to do so iscostly and time consuming.

An example of the above problem is the human eye. It is conventionallyassumed that ocular imperfections are limited to lower orderimperfections, including the imperfections commonly called “astigmatism”and “defocus”, that can be corrected by lenses having sphericalsurfaces. However, in reality optical systems including the human eyerarely are limited to what is conventionally assumed for purposes ofproviding corrective optics that have only spherical surfaces. In thecase of the human eye, for instance, higher order imperfections canexist, including but not limited to those imperfections known as “coma”and “trefoil”. These imperfections unfortunately cannot be corrected byconventional glasses or contact lenses, leaving patients with less thanoptimum vision even after the best available corrective lenses have beenprescribed.

Moreover, as recognized by the present invention, it is often difficultto simultaneously minimize all aberrations. Indeed, corrections to anoptical system to minimize one type of aberration may result in theincrease in one of the other aberrations. As but one example, decreasingcoma can result in increasing spherical aberrations.

Furthermore, it is often necessary to correct aberrations in an opticalsystem that are introduced during manufacturing. This process can beiterative and time consuming, requiring, as it does, assembly,alignment, and performance evaluation to identify aberrations, followedby disassembly, polishing or grinding to correct the aberrations, andthen reassembling and retest. Several iterations might be needed beforea suitable system is developed.

Having recognized the above-noted problems, the invention provides thebelow-disclosed solutions to one or more of them.

SUMMARY OF THE INVENTION

The present invention is related to optical elements having a variableand predetermined, three-dimensional spatial retardation distributionand related systems and methods for making such optical elements.

The optical element of one embodiment of the present invention includesa cavity. The cavity can be formed by a pair of transparent windows, orplates with a retaining ring, or spacer between the plates. The cavityis filled with one or more monomers, or pre-polymers, monomer mixturesand polymerization initiators (referred to generally herein as a resinmixture). This resin mixture exhibits an index of refraction change asit polymerizes, and the change is controlled by the extent of itspolymerization, or curing. The curing of the resin mixture may beinitiated by exposure to light, such as ultraviolet light. The exposureto light may be controlled spatially across and through the resinmixture to create a predetermined three-dimensional wavefrontretardation profile. One application of such a wavefront retardationplate is to cancel the aberrations in an optical system, such that whenan ideal plane wave passes through the wavefront retardation plate, apredetermined change of the wavefront profile can be affected by thewave plate, and when the wavefront subsequently passes through theoptical system, aberrations introduced by the system (except for theintended focusing of the system) are cancelled. Alternatively, if thegoal of the optical system is to establish a cylindrical lens, allaberration terms are cancelled, except for the desired astigmatismterms. Embodiments of the present invention have the ability to produceany retardation, including any one or any combination of the aberrationsas describable by the Zernike polynomials.

The present invention is also applicable to the manufacturing of allconventional and specialized optical elements, including aspheric andother refractive surfaces, refractive elements (e.g., lenses),reflective elements (e.g., mirrors and beam splitters), and/ordiffractive elements such as gratings, and Fresnel optics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a correcting element;

FIG. 2 is a schematic diagram of a first preferred apparatus forestablishing a correcting element;

FIG. 3 is a schematic diagram of a second preferred apparatus forestablishing a correcting element;

FIG. 4 is a schematic diagram of a third preferred apparatus forestablishing a correcting element;

FIG. 5 is a schematic diagram of a fourth preferred apparatus forestablishing a correcting element;

FIG. 6A is a schematic diagram of a fifth preferred apparatus forestablishing a correcting element;

FIG. 6B is a schematic diagram of a sixth preferred apparatus forestablishing a correcting element;

FIG. 7 is a cross-sectional view of corrective element shown in FIG. 1,taken along the line 7—7 in FIG. 1;

FIG. 8 is an enlarged view of a portion of FIG. 7;

FIG. 9 is a schematic top view of a typical curing pattern within theresin mixture layer of the correcting element, showing the location andrelationship between successive curing volumes within a layer of resinmixture;

FIG. 10 is a schematic elevational view of the correcting element shownin FIG. 1, showing a three-dimensional curing pattern profile consistingof multiple layers of cured resin mixture, and schematically showing thelight beams used to create the layers;

FIG. 11 is a flow chart of a process of forming a correcting element;

FIG. 12 is a schematic diagram of a wavefront;

FIG. 13 is a schematic diagram of an index of refraction profile forcuring a lens to compensate for aberrations shown in the wavefront ofFIG. 12;

FIGS. 14–16 show alternate configurations of the correcting element ofthe present invention;

FIG. 17 is a schematic diagram showing one of the correcting elements inone intended environment to correct aberrations in an optical system;and

FIG. 18 is a schematic diagram of an apparatus for measuring patientparameters.

DETAILED DESCRIPTION

Referring initially to FIG. 1, a correcting element of the presentinvention is shown, generally designated 10. As shown, the correctingelement 10 includes a first rigid or flexible transparent plate 12, asecond rigid or flexible transparent plate 14, and a layer of resinmixture 16 sandwiched therebetween. If desired, a barrier 18 can be usedto contain the resin mixture 16 between the plates 12, 14 prior to, andfollowing, the below-described curing of the resin mixture.

The term “resin mixture,” as used herein, is intended to includelight-curable resins comprised of one or more monomers, pre-polymers,polymers and polymerization initiators. The refractive index of theresin changes as the resin is cured, and it can be made to vary betweenlocations within the resin layer depending on the spatial extent ofcuring of the resin mixture, as more fully disclosed below. The extentof curing is determined by the percentage of cross-linking between themonomers within the resin mixture. One non-limiting example of suitableresins is VLE-4101 UV-Visible Light CureEpoxy, available from StarTechnology, Inc., or Optical Adhesive #63, U.V. Curing, available fromNorland Products, Inc. Typically, these resins are curable by exposureto UV or visible light radiation in the range of 300 to 550 nanometers(300–550 nm). Generally, any type of material that exhibits an index ofrefraction change upon curing may be used and the corresponding curinglight source may have appropriate curing wavelengths, e.g., wavelengthsthat are within the range of 250 nm to 3000 nm. Alternatively, the resinmixture can be cured by other radiation such as microwave or electronbeam.

It is to be appreciated, however, that many suitable resins exist whichexhibit a similar change in its index of refraction upon exposure tolight. Other monomers that polymerize into long-chain molecules usingphoto-initiators may be used. For example, a suitable monomer may bechosen from the family of epoxides, urethanes, thiol-enes, acrylates,cellulose esters, or mercapto-esters, and a broad class of epoxies.Also, for example, a suitable photo-initiator may be chosen from alphacleavage photoinitiators such as the benzoin ethers, benzil ketals,acetophenones, or phosphine oxides, or hydrogen abstractionphotoinitiators such as the benzophenones, thioxanthones,camphorquinones, or bisimidazole, or cationic photoinitiators such asthe aryldiazonium salts, arylsulfonium and aryliodonium salts, orferrocenium salts. Alternatively, other photoinitiators such as thephenylphosphonium benzophene salts, aryl tert-butyl peresters,titanocene, or NMM may be used.

As shown in FIG. 1, the second transparent plate 14 includes anoutwardly-facing curved surface 20 which may exhibit a pre-existingrefractive power. Alternatively, transparent plate 14 may be planar, asrepresented by the dashed line 22.

It is to be understood that the resin mixture 16 may be formed with apredetermined thickness “t” such that a predetermined volume isestablished between the plates 12, 14, and barrier 18. As understoodherein, the thickness and/or volume of resin mixture 16 can beestablished as appropriate to provide a correcting element having anydesirable spatial retardation distribution utilizing the index ofrefraction change of resin mixture in its cured state.

Referring now to FIG. 2, a system generally designated as 24, is shownfor curing the resin mixture 16 of the correcting element 10. As shown,the system 24 includes an X-Y-Z scanning unit 26 having an X-directionrail 28 and an Y-direction rail 30. Also, the system 24 includes aZ-direction rail 32 extending from the X- or Y-direction rails.Moreover, a light source 34 having a beam shaping unit 36 is attached toand is movable on the Z-direction rail 32. The beam shaping unit 36 mayinclude spatial filtering and beam collimation components to produce ahigher quality beam.

FIG. 2 shows that the light source 34, in combination with the beamshaping unit 36, create a light beam 38 which, in a preferredembodiment, is substantially collimated. It should be appreciated,however, that a non-collimated beam may also be used if desired. In oneexemplary, non-limiting embodiment, the light beam 38 passes through afocusing lens 40 to form a converging, or focusing, light beam 42 thatis directed toward the correcting element 10, where the light beam 42passes through the first transparent plate 12 to focus at 44 within theresin mixture layer 16, as shown and described further below inreference to FIG. 7. The focusing lens can be, e.g., a microscopeobjective piece with a large numerical aperture.

In any case, in accordance with present principles, the light source 34irradiates the monomer (e.g., resin mixture 16), which activates thephoto-initiator and begins the curing process within the resin mixture16. The curing process results in a corresponding change of the index ofrefraction within the resin. Terminating the exposure to the lightceases the curing of the resin mixture, thereby ceasing the change ofthe index of refraction exhibited by the resin mixture. In this manner,the correcting element 10 is established by exposing predeterminedportions of the resin mixture 16 to light.

As envisioned by the present invention, the activation and power levelof the light source 34 and its position along the X-Y-Z axes may becontrolled by a controller 46, which is electrically connected to thelight source 34 and to shuttling components on the rails 28, and/or 30,and/or 32. The controller 46 can receive instructions regarding thedesired index of refraction profile to be implemented from a computer 48with associated monitor 50. More particularly, by moving the lightsource 34 along the rails 28, 30, 32 in the directions respectivelyindicated by arrows 52, 54, 56, and by establishing the power of thelight source 34, curing volumes of differing sizes or the same sizes maybe formed within the resin mixture 16. For instance, by delivering alower intensity, or lower power level, from the light source 34, aspatially localized curing that is only immediately adjacent to thefocal point 44 can be established, to create a relatively small curingvolume. On the other hand, by delivering a higher intensity, or higherpower level, from the light source 34, a spatially localized curing mayinclude regions of resin mixture surrounding the focal point 44, tocreate a larger curing volume. Regardless, the depth in the resinmixture 16 of the focal point 44 is established by appropriatelyestablishing the distance d between focusing lens 40 and resin mixturelayer 16.

In a preferred embodiment, the power density of the light source 34 iscontrolled by controlling the current to the light source. Or, theamount of light delivered into the resin mixture 16 can be establishedusing a constant light source 34 power level and variable lightattenuator methods, including Pockel cells or other polarizationrotation means and a polarized discriminator. It is to be understoodthat other light intensity control methods can also be used.

In a particularly preferred embodiment, the scanning unit 26 first formsthe curing volumes which are farthest from the light source 34, i.e.,which are deepest in the resin mixture 16. For instance, the scanningunit 26 would initially position the focal point of the light beamadjacent the bottom plate 14. The advantage of initially curing theresin mixture furthest from the light source is that the curing statusof the entire resin mixture volume in the resin mixture layer 16 can bebetter controlled thereby. This method of photon energy delivery isparticularly advantageous in those cases wherein the cured resin mixturebecomes partially or substantially opaque at the curing wavelengthpost-curing, in which case the regions of the resin mixture 16 thatwould be behind the cured portion (i.e., furthest away from the lightsource 34) would otherwise become inaccessible for curing.

FIGS. 3 and 4 show related embodiments of another system, generallydesignated 60, that can be used to direct curing light onto thecorrecting element 10. A collimated light beam 62 is directed to a firstbeam scanner 64, which can be a single galvanometric type scanner forone dimensional scans as shown in FIG. 3. The light passes through afocussing lens 68 toward the target correcting element.

Or, two galvanometric scanners 64, 66 can be used as shown in FIG. 4,with their scan axes oriented orthogonal to each other, for generatingtwo dimensional scan patterns in the X-Y plane. The scanners 64, 66 areplaced close to each other and are positioned approximately at thepupilary plane of a focusing lens 68 with a focal length f1 , providinga focused spot in the resin mixture. Alternatively, one scanner ispositioned at the focal position of lens 68, at a distance of f1 fromthe lens, and a relay lens 70 with focal length f2 is positioned at adistance of f1+f2 from the focussing lens 68. Consequently, the lenses68, 70 establish a telescopic relay unit, with the second scanner unit66 being positioned at a distance of f2 from the relay lens 70. Ifdesired, an imaging lens 72 with focal length f3 can be positioned at adistance of f3 from the scanner 66, and the imaging lens 72 focuses thelight energy into a spot in the resin mixture volume.

In addition to the exemplary scanning units described above, it is to beappreciated that any three-dimensional beam scanning device includingthe use of rotating polygon, or resonance scanning mirrors as beamsteering elements can be used to direct and focus the irradiatingenergy.

Indeed, another embodiment of a system for delivering curing light tospecific locations in an resin mixture volume is shown in FIG. 5 andgenerally designated 74. The system 74 shown in FIG. 5 varies thelocation of the light source, shown at point 76, at the object plane,shown at 78. The system 74 includes, for the purpose of illustration,two lenses 80, 82 with focal lengths f4 and f5 , respectively, that arerespectively positioned a distance of f4 from the object plane 78 and f5from an resin mixture object plane 84. Also, the lenses 80, 82 areseparated from each other by a distance equal to the sum of their focalpoints (i.e., f4+f5 ). The radiation source indicated at 76 has acorresponding image point 86 at the resin mixture object plane 84.Likewise, for an off-axis light source location, e.g., as indicated at88 on the object plane 78, there is a corresponding point location 90 onthe resin mixture image plane 84. Accordingly, by moving the lightsource in the image plane 78 and by establishing an appropriate distancebetween the lenses 80, 82, the resin mixture of the present correctingelement can be cured at various depths at various locations asappropriate to establish a wavefront correcting element.

Still another system, generally designated 100, is shown in FIG. 6A. Asshown, a single light source 102 is positioned adjacent an optical fiber104, with the emitting, distal, end 106 of the fiber 104 being movableto various desired locations at the object plane of the resin mixture tobe cured. The positioning of the optical fiber is controllable bymechanical positioning means 107 that can include motorized translationstages that are movable in three dimensional (XYZ) space to focus lightat the target plane such that the radiation emitted from the fiber isdelivered to a corresponding image location at the image plane. In thisway, the photon energy is delivered through the imaging system to anydesired location in the resin mixture volume.

Alternatively, FIG. 6B shows a system 108 having a bundle of stationaryfibers 110, each carrying light from a respective light source 112. Theradiation intensity of each of source 112 is controllable by a computer.The fiber bundle configuration enables simultaneous multiple-pointcuring in the resin mixture, and therefore improves curing efficiencywithout compromising spatial resolution of the desired profile of theindex of refraction change in the resin mixture. After the curingprocess is completed for each location of the fiber bundle, the fiberbundle is then moved to a different location by mechanical translationmeans 113 to create the index of refraction profile in the resinmixture.

Having set forth various apparatus for selectively irradiating the resinmixture 16 of the correcting element 10 shown in FIG. 1, reference isnow made to FIGS. 7, 8, and 9, which show details of the resin mixturecuring process. As shown in FIG. 7, the converging light beam 42 passesthrough the transparent plate 12 and converges within the resin mixture16. Specifically, the light ray edges 42A and 42B of the beam 42converge at a focal point 114 and define a curing volume 116 (FIG. 8)that has a so-called “beam waist” 118. The beam volume 116 representsthe region in the resin mixture 16 which will be cured by exposure tothe converging light beam 42. More specifically, the relatively tightfocal point 114 of light beam 42 causes the spatially localized curingof the resin mixture 16 to form the curing volume 116. As set forthabove, the light beam scanning apparatus is operated to move the focalpoint of the light beam to various points in the resin mixture toestablish the desired curing pattern (light retardation) profile.Generally speaking, a beam 42 with a cone angle 119 that is in the rangeof 0.002 radians to 1.5 radians may be used.

FIG. 9 illustrates this. Because the preferred converging beam 42 in thepresent embodiment is conical in shape, the top view of each curingvolume 116 is circular. Looking at FIG. 9 it can be appreciated that aseries of light beams 42 may be used to form a continuous curing patternthrough the resin mixture layer 16. In the event that a continuouscuring pattern between successive curing volumes is desired, thedistance 120 between curing volumes should be less than the diameter,i.e., the waist 118, of the curing volume 116, thereby establishing anoverlap region 122 between adjacent curing volumes 116.

The size of the beam overlap region 122 can have a crucial effect on theoverall homogeneity of the index of refraction of the cured resinmixture 16. In a preferred embodiment, the size of the beam overlapregion 122 can vary between ten to seventy five percent (10%–75%) of thesize of the beam waist 118 of the adjacent curing volumes. In aparticularly preferred, non-limiting embodiment, the size of the beamoverlap region 122 is between forty to sixty percent (40%–60%) of thesize of the beam waist 118.

In one embodiment in which a tightly focused beam 42 configuration ispreferred, the beam waist 118 is in the range of twenty microns (20 μm)or less. However, beam waists between 0.1 microns and two hundredmicrons may be used. For the more demanding situations where the indexprofile is microscopic in dimensions, a diffraction limited focusingconfiguration with microscopic objective can be used. As an example, alight source can be used that produces a 350 nm wavelength light beam inconjunction with a beam focusing lens with a numerical aperture of 0.5.With this combination of structure, the beam waist 118 has a length ofabout 0.86 microns (0.86 μm) in air, and in an resin mixture with anindex of refraction of 1.54, as an example, the beam waist is 1.35microns, with the depth of focus being 0.87 microns below the surface ofthe resin mixture.

It is to be understood that the curing volumes 116 within the resinmixture layer 16 can be sequential and contiguous to each other as shownin FIG. 9, or the scan sequence may be randomly accessed, such that thenew curing location can be isolated from the previous location, with nooverlap of the beam waists.

In contrast to FIG. 9, which shows a schematic plan view of a curingprofile, FIG. 10 schematically illustrates an elevational view of theresin mixture to show an exemplary depth profile that can be achieved toestablish a three-dimensional curing pattern profile. As stated above inreference to FIG. 2, the deeper regions of the resin mixture 16preferably are cured first. This causes the formation of a curing volume124. The focal point of the light beam is then moved as described abovein the X-Y plane, thereby establishing a first cured layer 126 withinresin mixture layer 16. Then, the depth of the focal point of the lightbeam is adjusted and the light beam moved in the X-Y plane to establishadditional curing layers 128, 130, 132, 134, 136, 138.

Following the creation of a three-dimensional curing pattern profileshown in FIG. 10, excess, uncured resin mixture 140 may be removed fromthe correcting element 10 using a suitable solvent. Once removed, thevolume previously occupied by the uncured resin mixture 140 may berefilled with an optically stable fluid which exhibits no refractiveindex change when exposed to radiation. Or, the volume may be refilledwith same or similar resin mixture without any photo-initiator. Yetagain, the volume can be refilled with resin mixture containing curinginhibitor such as phenol, or hydroquinone derivatives, which wouldinhibit any curing action even the resin mixture is exposed toradiation. As still another alternative, the volume can be refilled withanother type of resin mixture having a desirable curing characteristicand with a predetermined index of refraction such that the final indexof refraction profile in the wave plate is reached when all resinmixture in the confined volume is substantially cure, and such thatexposure to sun light or other radiation shall not alter its refractiveindex profile. Still again, an optical coating can be applied on theplates 102, 104 to protect the resin mixture from exposure to apredetermined range of wavelengths that would otherwise cure the resinmixture.

By removing the uncured resin mixture and replacing its volume with orwithout an optically stable material, a stable correcting element 10 canbe established that resists changes to its index of refraction underlong term exposure to light sources. This is particularly useful inenvironments where the correcting element 10 would be exposed tosunlight or other light sources which might contain wavelengths whichwould cause further curing of the previously un-cured resin mixture 140.

FIG. 11 shows the overall steps set forth above. Commencing at block142, the aberrations, i.e., the wavefront, sought to be corrected isdetermined. To determine the wavefront, laser-based measuring techniquescan be used. In one exemplary, non-limiting embodiment, wavefrontsensing instruments such those manufactured by Visx, Santa Clara,Calif., or Zeiss/Humphrey Instruments, Dublin, Calif. can be used.

Referring briefly to FIG. 12, a wavefront 144 is shown that forillustration is a divergent wave which may consist of spherical,astigmatism and high order aberrations. At an imaginary cross sectionalplane 146, the wavefront has intersections located at points 148, 150,152, 154. The peak of the wavefront is indicated at 156, which istraveling ahead of the intersections 148, 150, 152, 154. The distancebetween the peak 156 and the intersections is typical expressed in theunits of physical distance in space. The peak 156 has a projected point158 on the plane 146.

Accordingly, the logic of FIG. 11 moves from block 142 to block 160 tomap the wave sought to be compensated to a resin mixture curing plan.The retardation profile can be determined, for example, by a computerwhich receives the determined wave front. The curing plan is used tocreate a curing profile that will vary the index of refraction of theresin mixture 16 to match the profile of the wave 144 such that a planewave exits the correcting device 10. An illustrative curing profile isshown in FIG. 13, which has a three dimensional distribution profile 162that is identical that of the profile of the wave 144 shown in FIG. 12.

Specifically, in one preferred, non-limiting embodiment, Softwarerunning on a computer would perform the following determination. Assumethat the unit of retardation required for an ideal compensation can becalculated as follows. Further assume that the difference Δn of theindex of refraction between cured and uncured resin mixture is known(typically in the range of 0.001 to 0.05). The maximum retardationrequired is the physical distance “d” between the wave 144 peak 156, andits projection point 158 on the plane 146. The required thickness of theresin mixture 16 consequently is at least d/Δn. In the curing profilefor the resin mixture layer 16, the scale of the magnitude of theretardation is such that the magnitude of thickness of the cured resinmixture or the integrated index difference at a profile peak 162 to itsprojection 164 on a cross-sectional plane 166 is d/Δn. The effect ofsuch a profile is that the peak 156 of the wave 144 will experience themost retardation, and the wave at the intersections 148, 150, 152, 154experience no retardation at corresponding locations 168, 170, 172, 174of the index profile which are in the uncured portion of the resinmixture 16. Accordingly, the resin mixture is cured such that it indexof refraction establishes a profile that matches the profile of the wavesought to be compensated for.

Once the desired refraction profile is determined at block 160, thelogic of FIG. 11 can move to block 176 to cure the resin mixture 16 inaccordance with the curing plan. As mentioned above, uncured resinmixture can be removed from the correcting element 10.

In certain embodiments the resin mixture 16 need not necessarily becompletely cured, depending on the curing plan. Partially cured resinmixture contributes less in the index of refraction change than acompletely cured resin mixture for the same volume. Furthermore, amixture of completely and partially cured resin mixture may also servethe purpose of wavefront compensation in one embodiment. It is theintegrated retardation index of refraction profile, and not the actualphysical shape of the cured resin mixture volume, that provides thenecessary compensation and retardation of the wavefront.

The foregoing systems and methods can be useful in providing a stableoptical wave plate which may exhibit any retardation level, with anyspatial variation. Embodiments are applicable to correct distortion in alight beam of any desirable cross sectional area, and have the abilityto correct not just low numbers of wave distortions in the range of afraction of a wave to a few waves, but to correct up to hundreds ofwaves, covering and area ranging from less than a millimeter to severalhundred millimeters. Embodiments are a stand-alone wavefront distortioncorrector, and can include a refractive power correction.

Indeed, turning to FIGS. 14–16, various other configurations of thecorrecting element can be seen. For example, as shown in FIG. 14, amirror 178 has a surface non-flatness of more than one wavelength at 632nm, generally considered to be of poor optical quality. To compensate, atransparent element 180, which is not necessarily of high surfacequality, is used as a cover, and a layer of resin mixture 182 is filledbetween the transparent cover 180 and the mirror 178. The wavefrontaberration of the combined elements is measured and mapped to a profileof a curing profile as described above to render a combined structurehaving a high optical quality with minimal aberrations. As an additionalimprovement, the outer surface of the mirror may be coated for UVblocking for stopping further curing and any change of the wavefrontprofile. Other methods of maintaining the index of refraction profiledescribed earlier are also applicable.

FIG. 15 shows an embodiment of the correcting element configured as alens 184. A transparent, nil-diffractive cover 186 can cover the lens184 and can have either a convex or a concave shape that closely matchesthe surface of the lens 184. Neither the lens nor the cover plate needhave a high surface quality tolerance. A layer of resin mixture 188 isdisposed between the cover 186 and the lens 184 to compensate forimperfections in the lens 184 in accordance with principles set forthabove.

Additionally, the embodiments of the present invention are particularlyuseful in the construction of improved ophthalmic lenses which haverefractive power established in increments of fractions of a wavelengthover the entire lens area, such that the lens produces localizedwavefront correction tailored to the aberration of the eye of anindividual. FIG. 16 shows such a correcting element.

In a preferred embodiment, the aberrations of an eye are measured asdescribed above. The outcomes of this wavefront measurement can includepiston, tip, tilt, defocus (spherical power), astigmatism and its axis,and the higher order aberrations describable in Zernike polynomials. Theprism (tip, tilt), spherical, and astigmatism components, which arereferred to as refractive powers, can be corrected with currentlyavailable ophthalmic lens with the best possible match, typicallylimited to ⅛ diopter increments. The systems described above are thenapplied to complete the correction of aberrations including the residualof the sphere and astigmatism and the high order aberrations. In FIG.16, a lens system 190 includes a conventional ophthalmic lens 192, acover lens 194, and a thin layer of resin mixture 196 disposedtherebetween. As an example, the conventional lens 192 can be a lenswith negative refractive power, typically for myopia patients, and theouter surface of the lens 192, i.e., the surface that is farthest wayfrom the eye, has less curvature than the inner surface. The cover lens194 may or may not have any focusing power, and it is preferably thin,to minimize the overall thickness of the combined lens system. It has asurface curvature closely matched with that of the outer surface of theconventional lens 192. The combined structure is then measured inaccordance with present principles to determine the overall refractivepower and aberration including the cover lens 194 and resin mixture 196.This is mapped to a curing plan for the resin mixture 196 by subtractingfrom the eye measurement the correction and aberration of the combinedlens structure to render a residual aberration profile. Then the resinmixture 196 is cured to create an index of refraction profile accordingto the residual aberration profile to cancel the residual aberration.The area of the ophthalmic lens 190 can be in the range of 3 mm to 70mm, and not usually less than the pupil size of the patient. The opticalcenter of the lens 190 is then aligned with the entrance of the pupillocation on a spectacle frame, and the lens 190 is then cut to thecorrect size to fit into the spectacle for the patient.

Another application of embodiments of the present invention areimproving the resolution of viewing instruments such as telescopes,microscopes, ophthalmic diagnostic instruments including confocalscanning ophthalmoscopes, and fundus cameras. In all cases, each viewinginstrument includes refractive elements such lenses, reflective elementssuch as mirrors and beam splitters, and diffractive elements such asgratings and acousto- and electro-optical crystals. The presentinvention can eliminate costly manufacturing of such apparatus by usingless costly optics and by compensating for the attendant residualaberrations with correcting elements such as are described above.

The aberrations of the selected optical system are first analyzed andmeasured and then mapped to a resin mixture curing plan for anappropriately configured correcting element, which cancels the wavefrontaberrations of the optical system. The optical system being correctedcan, if desired, include the aberrations introduced by a particularuser's eye, so that these aberrations are also compensated for. In thecase of a telescope, a correcting element of the present invention ispositioned next to the objective lens of the telescope, where the imagerays are approximately collimated. In the case of microscope, acorrecting element is positioned next to the eyepiece.

In the case of fundus camera, which is compensated for similarly tomicroscope compensation, aberrations of the patient's eye to be examinedmay limit the resolution of the camera. If so, a correcting element ofthe present invention is first constructed to cancel the aberrations ofthe eye under cycloplegia conditions wherein the accommodative musclesof the eye are paralyzed, and a separate correcting element for thecorrection of the aberrations of the camera is constructed and ispermanently attached to the camera.

FIG. 17 shows how a correcting element can be incorporated into aconfocal scanning imaging system 200. A collimated light beam 202 from,e.g., a diode laser or a HeNe laser 204, is directed by a beam splitter206 to a beam scanner unit 208. The beam splitter 206 can be a 50–50beam splitter or a polarization beam splitter which has an appropriatecoating to maximize the reflectivity for the incident and maximizedtransmission for the returned beam with the appropriate polarizationcharacteristics. The scanner unit 208 has its scanner mirror 210positioned at the focal point of a focusing lens 212, which has a focallength of f10. The scattered light at a target point 214 is imagedthrough the lens 212, reflected by the scan mirror 210, and focused by asecond lens 218 onto a pin hole 218. The light intensity is detected bya detector 220, and is recorded at each target position and processedfor the reconstruction of a profile of the target. For two dimensionalscanning, two additional relay lenses and a second scanner are insertedbetween the first scanner 208 and the focusing lens 212.

To attain improved performance of the system 200, a correcting element222 in accordance with the foregoing teachings is positioned in thelight path to correct the wavefront aberrations introduced by one ormore of the above-mentioned components. Likewise, a correcting elementcan be positioned in the light path if desired.

Now referring to FIG. 18, another application of an embodiment of thepresent invention is to provide customized progressive addition lenses(PAL) for presbyopic patients. Current progressive addition lenses havea fixed distance between the optical center for the distant vision andthat of the near vision. Typically, the patient is fitted for thedistant vision for a specific glasses frame of patient's choice. Thepatient must adapt to a specific viewing angle, by tilting of the headin order to find the best viewing angle for the near vision. This makesthe experience of wearing the progressive addition lens unpleasant for aperiod of weeks or up to several months before the patient becomesaccustomed to the lens.

With the above considerations in mind, a video image capture setup asshown in FIG. 18 can be used to capture the point of intercept of thepatient's visual axis with a lens 922 in a trial frame 924 or in a frameselected by the patient. A video camera 910 is positioned at about 90degrees from the line of sight 920 towards a standard test eye chart930, and a beam splitter 940 is positioned in the line of sight and isoriented at about 45 degrees to direct an image en face to the patient'seye and the spectacle frame to the camera 910. The camera and the beamsplitter can be positioned at any convenient location between thepatient and the test eye chart. When the patient is examined in dimlight conditions, additional near-infrared illumination at wavelengthslonger than 700 nm may be applied to illuminate the eye for ensuring anadequate signal to the camera. The beam splitter may be coated for hightransmission for the visible spectrum and for high reflectivity at thenear infrared wavelength at 45 degrees. Depending on the location ofchoice of the camera, a zoom lens may be part of the focusing elementsof the camera to bring in the image of the eye and the eyeglasses frameto sufficiently fill the image sensor of the camera.

The camera 910 first captures the location of the center of the pupilrelative to the bottom of the eyeglasses frame when the patient islooking at a distant object (eye chart) 930. A second camera 960positioned and pointed at the side of the patient head (90° en face)captures the tilt angle of the patient's head when the patient isreading a distant chart or object. The patient is instructed to view thedistant object in a most comfortable and natural position. At thatpoint, either the patient or the examiner pushes a switch in a triggercontrol 970 connected to the cameras 910 and 960 to record the relevantpositions and angles in video images from the cameras 910 and 960.

For the near viewing measurements, the patient is then asked to read abook page, which is disposed at his natural reading position. Dependingon the patient's need, the patient instead may be asked to view adisplay on a computer monitor. The camera 910 captures the change in theconvergence of the eyeballs when patient is reading at a near distance.The camera 960 now captures the head tilt angle and the distance betweenthe apex of the cornea to the spectacle lens, using a zoom feature ofthe camera, and the position of the reading material at the near viewingposition without camera zooming. To more accurately pinpoint thepatient's line of sight at the near viewing, the patient may beinstructed to hold a printed page 990 and read a line at the center onthe printed page, and the reading material can be sufficiently reducedin size to reduce variability. The tilt angle of the head can be deducedfrom the landmarks on the patient's head/ear, or two markers 980, 985can be placed on the patient's head in near vertical alignment with aheadband 987 for example.

Data analysis from the video images identify the tilt angle of the headat both distant viewing and near viewing, and the angle of the line ofsight of the near viewing relative to that of distant viewing. Thedifferences of the angles between the lines of sight and the respectivetilt angles of the head correspond to the amount of eye rotation whenthe patient changes from distant to near viewing. From the apex distanceof the spectacle lens, and the angle of the eyeball rotation, the actualdistance between the distant optical center and the near optical centeron the spectacle lens can be determined. This distance is unique andcustomized to the patient, since such a separation distance of theoptical centers of the near and distant zones on the spectacle lens andtheir locations are customized for the natural reading and viewinghabits of the patient, and the pupilary distances at the distant andnear viewing.

The foregoing teachings are then applied to construct the added power ofthe progressive addition lens for the near viewing to the ophthalmiclens, using customized locations of the optical center for the distantviewing and the optical center for the near viewing for that patient.The design of the added power for a progressive addition lens is wellknown in the art. Alternatively lens design services can be obtainedthrough lens providers such as Shamir Optical of Israel. The powerprofile of the progressive addition lens is then converted into theindex of refraction change profile in the resin mixture layer. Thiseliminates the process which current progressive addition lensmanufacturing requires, i.e., the making individual molds for eachcustomized configuration.

While particular embodiments and examples are shown and described indetail herein it is to be understood they are representative of thesubject matter which is broadly contemplated by the present invention,that the scope of the present invention fully encompasses otherembodiments which may become obvious to those skilled in the art, andthat the scope of the present invention is accordingly to be limited bynothing other than the appended claims

1. A method for manufacturing a correcting element having at least onetransparent element, and a layer of curable, refractive index changingmaterial adjacent to the at least one transparent element, comprising:obtaining a three-dimensional index of refraction profile; focusing aradiation beam on a first location within the material layer toestablish a first curing volume within the material layer; andrefocusing the radiation beam on one or more subsequent positions withinthe material layer to establish one or more additional curing volumes,wherein the first curing volume and the subsequent curing volumescollectively establish the three-dimensional index of refractionprofile, wherein at least two curing volumes occupy different depthpositions within the material layer.
 2. The method of claim 1, whereinthe first curing volume and the subsequent curing volumes are located intwo or more curing layers having different depths within the layer ofmaterial.
 3. The method of claim 1, further comprising: determiningaberrations in a wavefront; and determining the three dimensional indexof refraction profile to compensate for at least some of theaberrations.
 4. The method of claim 1, wherein forming the first curingvolume and the subsequent curing volumes further comprises exposing thematerial layer to a light beam having a wavelength suitable for curingthe material layer.
 5. The method of claim 1, further comprisingstabilizing the curing of material layer after the profile has beenestablished, the act including removing uncured material from thematerial layer to establish at least one cavity and undertaking at leastone of: (1) refilling the cavity with an optically stable fluid whichexhibits no refractive index change when exposed to radiation; (2)refilling the cavity with the same or similar material without anyphoto-initiator; (3) refilling the cavity with material containing acuring inhibitor; (4) refilling the cavity with another type of materialhaving a desirable curing characteristic and with a predetermined indexof refraction such that the final index of refraction profile in thewave plate is reached when all the material in the cavity issubstantially cured; (5) adhering cured material to the at least onetransparent element; and (6) applying highly absorptive or highlyreflective coatings on the surface of the at least one transparentelement to protect the material layer from exposure to at least somelight.
 6. The method of claim 1, wherein the curing volumes are exposedto a focused light beam sequentially such that curing volumes positionedfurther from a source of said focused light beam are exposed prior tocuring volumes positioned closer to said source of said focused lightbeam.
 7. The method of claim 1, wherein the first curing volume and atleast one subsequent curing volume occupy adjacent locations in a singlecuring layer within the layer of resin mixture.
 8. The method of claim7, wherein the first curing volume and the at least one subsequentcuring volume occupy overlapping positions in the single curing layersuch that the distance between center portions of the first curingvolume and the at least one subsequent curing volume is less than adiameter of a beam waist of the first curing volume or the at least onesubsequent curing volume.